Process for preparing vinylaromatic sulfonic acid salts



SUFONIC AClD SALTS Chaines T. Goodshaw and Charles E. Qrabiel, Midland, and Henry Volk, Boy City, Mich., assignors to The Bow Chemical Eompany, lidland, Mich., a corporation of Belawai'e Filed Get. 29, 195%, Ser. No. 779,542 4 Claims. (Cl. 26d-595) This invention concerns an improved method for making nuclear sulfonated vinylaromatic compounds and their alkali metal salts having the general formula Cll2=CH-Ar-SO3M, wherein Ar represents an aromatic group containing from 6 to 8 carbon atoms, and M represents H or an equivalent of an alkali metal.

in the known preparation of such compounds by reacting together approximately equimolar amounts of sulfur trioxide and a -haloethylaryl compound and treating the resulting -haloethylaryl sulionic acid with an alkali to dehydrohalogenate the same and form a salt of the vinylaryl sulfonic acid thus formed, several disadvantages have been noted. First, considerable sulfone by-product is formed. Such sulfone by-product is worthless and must now be discarded. its formation is catalyzed by boron oxide present as a stabilizer in commercial liquid sulfur trioxide, widely used in sulfonating -haloethylaryl compounds. Second, an appreciable amount of lay-product vinylaryl sulfonic acid anhydride is formed, i.e., from about l to 30 weight percent, -haloethylaryl basis. Third, the conventional method leaves considerable unreacted haloethylaryl compound. Fourth, in water-extracting the vinylaryl sulronate from the reaction medium conventionally containing inert polychlorinated aliphatic hydrocarbon solvent, the conventional way for separating intermediate product from sulione, an appreciable amount of sulfonic acid is thereby lost since it is somewhat soluble in the water-wet polychlorinated aliphatic hydrocarbon. Fifth, polymer formation in the dehydrohalogenation and sulfonate recovery operations reduces product yield and plugs reactors. The known method, therefore, usually gives approximately a 55 percent maximum yield or nuclear sulionated vinylarornatic sulfonic acid and salts, based on -haloethylaryl reactant.

It has now been discovered that the disadvantages ci the prior art can be overcome and the yield of nuclear sulfonated vinylaryl compounds and their salts can be raised to about S percent and higher by (l) reacting toget er at least an equimolar proportion, and preferably an excess, of unstabilized (boron oxide-free) sulur tr`- oxide and a -haloethylaryl compound in solution in an inert polychlorinated aliphatic hydrocarbon solvent, i.e. from about 1.0 to about 2.0 rnole equivalents of sulfur trioxide per mole of -haloethylaryl reactant, (2) allowing the resultant sulfonation reaction mixture to stand for a period of tinte up to about 4 hours until substantially maximum sulfonation has been attained, (3) then adding from about 0.5 to about 5 weight percent of water, theoretical sulonic acid basis, dependent upon the amount orexcess S03 used, to hydrolyze by-product sulfonic acid anhydride to sulfonic acid, (4) adding excess aqueous caustic to form sulonate salt, to neutralize excess acid and to neutralize hydrogen halide evolved on subsequent dehydrohalogenation, (5) ila-sh distilling.,7 off the inert solvent, (6) removing any insoluble matter from the remaining solution, (7) heating the remaining aqueous phase until dehydrohalogenation is substantially complete in tbe presence of air or oxygen to prevent polymer formation, (S) neutralizing excess base, and (9) recovering vinylaryl sulonate product, as by spray drying or crystallization. The process is illustrated in the accompanyirv7 diagrammatic llow sheet.

he -haloetnylaryl compounds which are employed as starting materials in the process of this invention have the general formula Ar-CH2-CH2-X, wherein Ar is an aromatic group containing from 6 to 8 carbon atoms and X is chlorine or bromine. Exemplary of such compounds are -chloroethylbenzene, -bromoethylbenzene, a-methyl--bromoethylbenzene, a methyl--chloroethylbenzene, ar-(-chloroethyDtoluene, ar bromoethyl) toluene, ar-( bromoethyl)xylene, ar-( chloroethyl) mesitylene, ar-(-bromoethyl)mesitylene, IB-chloroethylnaphthalene, bromoethylnaphthalene, ,B chloroethylchlorobenzene, -bromoethylchlorobenzene, -brornoethylbromobenzene, -bromoethyldichlorobenzene, -chloro ethyldichlorobenzene, etc.

The -haloetbylaryl compound is sulfonated by treatment with about 1.0 to about 2.0 times its molar equivalent of sulfur trioxide at a temperature between about -20 and 80 C. Below 1.0 mole equivalent of sulfur trioxide per mole of -haloethyl compound, reaction tends to be incomplete within a reasonable time, while larger amounts than 2.0 mole equivalents of sulfur trioxide are uneconomic. The reactants can be mixed in any order, e.g., by pouring the aryl reactant into a liquid body cornprising the sulfur trioxide or causing separate streams to flow together at rates such as to form a mixture of reactants in the indicated proportions. The sulfur trioxide is preferably fed into a liquid stream comprising the ,-haloethylaryl reactant in a continuous process so as to maintain at least an equimolar proportion of reactants at all stages of the reaction. The reaction mixture is advantageously stirred or otherwise agitated during reaction. The sulfur trioxide is used in liquid or vapor form, diluted or undiluted, when fed to the sulfonate reaction. Suitable diluents include nitrogen, liquid or gaseous sulfur dioxide, aud liquid polychlorinated aliphatic hydrocarbons as described below.

The ,B'haloethylaryl compound is in solution when subjected to sulfonation, e.g., from about l to about Weight percent solution and preferably from 4about 5 to about 30 percent in a liquid polychlorinated aliphatic hydrocarbon, such as carbon tetrachloride, ethylene dichloride, chloroform, methylene chloride, etc. Methylene chloride is preferred.

The optimum reaction conditions are dependent upon variable factors, such as the kind and amount oi diluent present in the reaction mixture, the mode of admixing the reactants, and the reaction temperature, certain of which variable factors are interdependent. Sulfur trioxide is capable of reacting not only to sulfonate the lialoethyl aromati-n compound in the desired manner, but also to form sulione by-product such as bis-(-brornoethylphenyl) sulfone and bromoethylbenzene sulionic anhydride. lt is also capable of reacting to an appreciable extent with liquid polychlorinated aliphatic hydrocarbons such as are usually employed as media for the reaction, to form other undesired by-products. The reactions to dorm 'oy-products occur more extensively as the reaction temperature is raised, especially above 59 C. The reaction -to form an organic sulfone also occurs more extensively with increase in the concentration of therectants :in the reactionl mixture and is suppressed by carrying the reaction out in the presence of one or more of the aforementioned liquid diluents.

For these reaso-ns the sulfonation is usually carried out at temperatures between about 10 and 50 C. by feeding sulfur trioxide in liquid or vaporized form into a solution or" the lB-haloethylarornatic compound in one or more of the aforementioned liquid solvents while stirring or otherwise agitating the resulting mixture. However, by suitable balance between lthe above-mentioned variable reaction conditions, the sulionation can be carried out at somewhat lower or higher temperatures, eg., Vat temperatures of 20 to 80 C. The su-lfonation is usually accomplished at atmospheric pressure or thereabout, but it can be c-arried out in a closed reaction system at pressures up to 100 pounds per square inch gauge or above.

The sulfonation medium is held for a period of time, usually about 2 to 4 hours until substantially maximum sulfonation has been attained, as determined by testing an aliquot. This holding period at reaction temperature has been found to decrease unreacted -haloethylarornatic reactant to a maximum of less than 5 percent of charged haloethylaromatic compound.

After `attaining maximum reaction by the indicated holdup, a quantity of about 0.5 up to about 5 weight percent of Water, based on theoretical sulonic -acid formed, and depending upon the amount of SC3 reacted, is then added. lt converts the sulfonic acid Vanhydride by-product to the wanted sulfonic acid.

Aqueous caustic, advantageously in excess, as a 50 weight precentsolution, together with water sulcient to `give Ythe desired lnal concentration of product, is then added to the reaction medium, advantageously irst cooled to room temperature, in amount of about 2.1 molar proportions of caustic per mole of Yadded sulfur trioxide, to form sulionate, to neutralize excess acid and to neutralize hydrogen halide Vto be lliberated in the dehydrohalogenation reaction.

The alkaline reaction medium is then ash distilled to Aremove solvent. The distillation also serves to hydrolyze any remaining by-product sulfonic acid anhydride to the desired sulfon'ate. Previously, sulionic acid has been extracted from polychlorinated solvent by means of water. Because ofthe solubility of the sulfonic acid solution in the thereby water-wet polychlorinated solvent and because of poor separation of phases, as much as percent of the sulfonic acid has been lost in the solvent phase by this prior art method.

Any insoluble matter remaining in the reaction medium after the solvent stripping is removed, advantageously by lsettling o-ut in a settler or by ltration, and the intermediate sulfonate in the alkaline reaction medium is then dehydrohalogenated by heating to a temperature between about 50 and 100 C., advantageously for between about 1A and 1/2 hour. genation, .air or oxygen is bubbled through to minimize polymer formulation. f

After dehydrohalogenation is substantially complete, as determined by testing an aliquot, excess base is neutralized, advantageously by adding mineral acid, and the vinylaryl sulfonate product is recovered by spray drying or by crystallization.

The following examples are in illustration of and not in limitation of the invention, which is dened in the claims.

Example L Contnuous Preparation of Sodium Styrene Sulfomzte A quantity oi 50.6 lb./hr. of 2-bromoethylbenzene and 540 llb./hr. of methylene chloride -at 25 C. were pump-l ed continuously into a stainless steel mixer reactor. Commercial grade anhydrous liquid sulfur trioxide con- During the dehydrohalotaining ca. 5 weight percent boron oxide stabilizer was pumped into ya distillation unit at the rate of 23.4 lb./hr. and the boron oxide-free S03 vapors were fed to the stainless steel mixer reactor where sult'onation took place. The molar proportion of S03 to 2-bromoethylbenzene Was about 1.1 to 1. The temperature of the resulting 2- bromoethylbenzene sulifonic acid solution leaving the mixer reactor was 55 60 C. The sulfonic acid solu- -tion was then passed intoV the bottom of a `glass-lined holding column of such capacity to provide on the average of 3 hours retention time to'complete the sulfonation reaction. The solution was then passed to a second stainless steel tanl; Where 0.67 llb./hr. of Water were introduced to aid in the hydrolysis of the p-(2-bromoethylphenyl) sulfonic acid anhydride by-product to 2-bromoethylbenzene sulfonic acid. After passing through this second tank (which provided on the average of 2 hours retention time), the sulfonic acid solution was passed to a Ystainless steel pipe mixer where it was contacted with a suicient amount of water to give a 10 percent solution of the finished sodium styrene sulfonate. Also introduced at this point was a sulicient amount of vaqueous 50 percent sodium hydroxide to provide 2.1 equivalents of base per equivalent of total'acid in the sulfonic acid solution. After passing through the pipe mixer, the combined streams were sent to a jacketed, steam-heated stripper column which was heated to 48 C. The methylene chloride was dashed oil overhead to a cooler and water separator and then recovered for a recycle. The aqueous phase passed downstream to a jacketed, cooled, stainless steel, settlingdrum where any solids or unreacted 2-bromoethylbenzene were separated. The -aqueous phase was then passed tothe bottom of a dehydrobrominator, which consisted -of Ia bathed,V agitated, stainless steel tank which was jacketed and heated with steam to 82-86 C. Als-tream of air was sparged into the solution as it entered the bottom of the tank to minimize polymerization of the sodium styrene sulfonate as vit formed. After an average of one hours retention time in the dehydrobromiu-ator, the sodium styrene sulfonate solution was passed to a cooling tank where it was cooled to'room temperature. The cooled solution was ltered in the presence vof lter aid, then passed to a neutralizer where it was neutralized to pH 7.5 with concentrated sulfuric acid. After adding inhibitor, the aqueous l0 percent solution of sodium styrene sulfonate (85 percent yield, 2bromoethylbenzene basis) lwas spray dried in' a Nichols hot air spray drier. The spray dried material analyzed sodium styrene sulfonate, 48-54 percent, and sodium bromide, 27-33 percent.

Example 2.--Bnch' Preparation of Sodium Styrene Sztl'fonate A quantity of 92.5 grams (0.5 mole) of 2-bromoethylbenzene and 723 g. of methylene chloride was placed in a 2-liter, S-n'ecked flask which was equipped with a water cooled condenser, stirrer and dropping funnel. tity of 25 ml. of distilled, anhydrous, boron oxide-free sulfur trioxide (0.6 mole) was dissolved in 432 g. of methylene chloride and added to the above dropwise with good agitation over a S-minute period. The temperature went from 20 .to 40 C. during the addition of the sulfur trioxide. -Stirring Was continued for an additional l0 minutes. The sulfonation mixture was poured into a stirred, 3-liter, S-necked ilask which contained a solution of 59.6 g. (1.5 mole) of sodium hydroxide in 927 g. of Water. The methylene chloride was distilled from the mixture at atmospheric pressure, and .the aqueous phase was then heated at to 97 C. for 0.5 hour. Air was sparged through the charge during the dehydrobromination. The aqueous phase was analyzed and found to contain 8.66 percent sodium styrene sulfonate which was equivalent to a 92.1 percent yield, Z-bromoethylbenzene basis.

A quan- Y Example 3.-Bzzclz Preparation of Sodium Vinyltolllelle Sulfonate A quantity of 99.5 g. (0.5 mole) of mixed isomers of 2bromoethyltoluene and 810 g. of methylene chloride was placed in a 2-liter, B-necked llask which was equipped with a water cooled condenser, stirrer and dropping funnel. A quantity of 25 ml. of distilled anhydrous sulfur trioxide (0.6 mole) was dissolved in' 432 g. of methylene chloride and added vto the above by means of a dropping funnel with good agitation overa 6-minute period. The temperature Went from 25 to 40.5 C. during the addition of the sulfur trioxide. After stirring an additional 10 minutes, the sulfonation mixture was poured into a 3-liter, 3-n'ecked tlask which contained a solution of 58 g. (1.45 moles) of sodium hydroxide in 990 g. of water. The methylene chloride was distilled off at atmospheric pressure and the aqueous phase was then heated with stirring at 80 C. for 0.5 hour. The solution was analyzed and found to contain 8.03 percent sodium vinyltoluene sulfonate. This was equivalent to -an 85 percent yield, 2-bromoethyltoluene basis.

Some of the `water was evaporated from the dehydrobrominated solution and the resulting precipitate iiltered oil and vacuum dried at room temperature. A'White crystalline product was obtained, analyzing 90.8 percent sodium vinyltoluene sulfonate.

Example 4.-Bztclz Preparation of Sodium Diclzlorostyrcne Szalfonate A quantity of g. of mixed isomers of diehloro(2 oromethyDhenzene and .171 g. of methylene chloride was placed in a 500 ml. 3-necked flask equipped With a condenser, stirrer and dropping funnel. To the Iabove was added by means or a dropping .ffun'nel 8.2 ml. (15.7 g.) of distilled boron oxide-free sulfur trioxide dissolved in 141 g. of methylene chloride. The molar proportion of S03 to dichloro(2-bromoethyl)benzene was 2 to 1. The addition required 5 minutes. The temperature rose from 20 to 33 C.

After standing overnight, the resulting sulfonate was dehydrohrominated in the following manner: 450 g. of water and 16.6 g. of sodium hydroxide were placed in a l-liter, 3necl ed ilask equipped with an air sparger, stirrer, heating mantle and thermometer. To .this was added the sulfonation solution. The methylene chloride was flashed ol and the aqueous phase was heated 0.5 hour at 80 C. Air was sparged into the charge during the dehydrobromination'. A 93 percent yield of sodium dichlorostyrene sulronate was obtained vbased on the charged bromoethylbenzene. When the preparation was repeated with a 20 percent molar excess of sulfur trioxide, the yield of sodium diohlorostyrene sulfonate was reduced to 75.2 percent.

Example 5.-E1ect of Boron Oxide On Formation of p,pBis(2-Bromoell1ylplrenyl) Sulfone a-Bromethylbenzene was sulfonated batchwise with Sultan B (commercial grade sulfur trioXide), stabilized with about 5 percent boron oxide) and with distilled Sulfan B free of boron oxide. The results in following Table I show that formation of the undesired p,p-bis(2bro moethylphenyl) sulfone is catalyzed by the presence of the boron' oxide stabilizer' in Sulfan B. When distilled Sulfan B was used in the sulfonation, only 1.3 to 1.9 er cent sul'fone was formed based on Z-bromoethylbenzene as compared with 6.5 percent when using Sulfan B. Also, when 3.9 weight percent additional boron omde was added to Sultan B, the yield of sulfone was increased to 13.7 percent. A 7.4 percent yield of sulfone was ohtained when 5.5 Weight percent boron oxide Was added to distilled Sulfan B.

The typical procedure used for the sulfonations is as follows. A quantity of 57.4 g. (0.31 mole) of Z-bromo- TABLE I Eecl of Boron Dxio'e on Suljonea Formation BEBb MeClgu S03, Broad, Percent Run (gms.) (gms.) m1. Type S03 percent yield sulfone 1 57.4 610 26.5 Sulfan B ea..5 6.5 57.4 610 26.5 dO ca.8.9 13.7

57.4 610 26.5 Distilled 0 1.9

57.4 610 14.2 ---do 5.5(added) 7.4

e p,pbis(Q-brornoethylbenzene) sulione.

b 2-bromoethylbenzene.

Methylene chloride.

d Percent B203 based on S03.

e Percent yield based on 2-bromoethylbenzene.

Example 6.Extmction 012-Bron'zoethylbenzene Sulfonc Acid and p-(2-Bromoetlzylplzenyl)Sulfonic Acid Anhydrde From a Metlzylene Chloride Solution of Sulfomited Z-Bromoelzylbenzene An improved yield of Z-bromoethylbenzene sulfonic acid was obtained, as shown in following Table Il, when the sulfonation solution was extracted by ash distilling the methylene chloride in the sulfonation solution from an aqueous caustic solution. The increased yield was due to complete removal of all the sulfonic acid as Well as the hydrolysis of the p-(2-bromoethylphenyl)sulfouic acid anhydride which is also formed during the sulfonation reaction. Simply extracting the sulfonation solution by stirring with water (the prior art method) does not effectively cause hydrolysis of the water insoluble anhydride nor does it completely remove all of the sulfonic acid. Although the yield of 2-bromoethylbenzene sulfonic acid was increased 7 percent when the stirring time was increased from 5 to 33 minutes, the flash method gave still another 32 percent increase. Foll Wing is a description of a typical procedure used in extracting the 2- romoethylbenzene by: (l) stirring the sulionation solution in the presence of water, and (2) the Hash method.

(l) A l-liter sample of sulfonation solution talren from the sulfonation mixer reactor during a continuous run, as described in Example 1, was extracted by stirring with 500 ml. of water for a predetermined tine. The water extract was then placed in a l-liter tlask equipped with a stirrer, thermometer and heating mantle. To this was added 67 g. of sodium hydroxide (2.1 equivalents of sodium hydroxide per equivalent of total acid in the water extract). After heating 0.5 hour at C., the solution was analyzed for sodium bromide and sodium styrene sulfonate. The yield of 2-brornoethylhenzene was based on the sodium bromide formed.

(2) A l-liter duplicate sample of sulfonation solution as in preceding part (l) was added to 567 g. of aqueous 11.8 percent caustic which was contained in a 2liter ilasli equipped with a stirrer, thermometer .and heating mantle. Suiicient caustic was present to provide 2.1 equivalents per equivalent of total acid in the sulfonation solution. T he methylene chloride in the sulfonation solution was then ash distilled and the aqueous phase was heated 0.5 hour at 80 C. The solution was analyzed and the yield of Z-bromoethylbenzene sulfonic acid determined as described under (l).

TABLE lI Comparison of Extraction Methods Sulfona- Molar Extraction Contact Yield,* ratio, tionl Run Method solution, time BEB- NaSS/ Veiml. H2O] (mins.) SOsH NaBr ciency ml. Y (percent) (i) 0.5 33 0.0694 i. 00 70 10 3..--- (2) O. 5 0.0989 O. 95 100 CODE:

BEB-SOzB'. =2bromoethylbenzene sulfonic acid. NaSS=Sodium styrene sulfonate. Sulfonation so1ution=A methylene chloride V'solution of sulionated fbromoethylbenzene.

(1) The sulfonation ysolution was extracted with water. (2) The sulionation solution and aqueous caustic were combined and the methylene chloride was then flash distilled ott.

*The yieldY is expressed in grams BEB-SOH/g'tam of sulfonation solution and is based on the sodium bromide 'formed after dehydrobrominating the extract by heating at 80 C, for 0.5 hour.

The estraction eiciency of runs 1 and 2 was based on run'3.

to obtain substantially the maximum yield of resulting -haloethylaryl sulfonic acid, adding a small amount of water from 0.5 to 5 weightvpe-rcent, theoretical snlfonic acid basis, sutcient to hydrolyze by-product sulfonic acid anhydride, adding to the reaction medium excess aqueous yalkali over that required to vneutralize excess sulfonation acid, sulfonic acid product and to neutralize hydrogen halide which results from dehydrohalogenation of the -haloethylaryl sulfonic acid, in amount of the' order of 2.1 moles of alkali per mole of added sulfur trioxide, water present being in amount su'icient to Vgive the desired solution concentration of iinal product, distilling oi the polychlorinated 'aliphatic liquid hydrocarbon, separating insoluble matter from the remaining mixture of reaction medium and aqueous alkali and heating the resulting aqueous mixture at about to about 100" C. while oxygen is tbubbled therethrough-to minimize polymer formation until dehydrohalogenation is substantially complete.

2. Method of claim 1, wherein the -haloethylaroma'tic compound is V2-'hromethy'lbenzene.

3. Method of'claim l, `wherein the Y,ei-haloethylaromatic compound is a 2bromoethyltoluene.

y4. Method of claim 1, wherein the -haloethylaromatic compound is a dichloro(2bromethyl)-benzene.

References Cited'i'n the fiile of this patent UNITED STATES PATENTS 2,821,549 Mock Ian. 28, 1958 

1. A METHOD FOR MAKING A SALT OF A VINYLAROMATIC SULFONIC ACID BY SULFONATING A B-HALOETHYL AROMATIC COMPOUND CONTAINING FROM 8 TO 10 CARBON ATOMS IN SOLUTION IN A POLYCHLORINATED ALIPHATIC LIQUID HYDROCARBON BY REACTION WITH APPROXIMATELY 1.0 TO 2.0 TIMES ITS MOLAR EQUIVALENT OF PURIFIED SULFURE TRIOXIDE AT A REACTION TEMPERATURE BETWEEN ABOUT -2:* AND 80* C., HOLDING THE REACTION MIXTURE FOR A TIME SUFFICIENT, UP TO ABOUT 4 HOURS, TO OBTAIN SUBSTANTIALLY THE MAXIMUM YIELD OF RESULTING B-HALOETHYLARYL SULFONIC ACID, ADDING A SMALL AMOUNT OF WATER FROM 0.5 TO 5 WEIGHT PERCENT, THEORETICAL SULFONIC ACID BASIS, SUFFICIENT TO HYDROLYZE BY-PRODUCT SULFONIC ACID ANHYDRIDE, ADDING TO THE REACTIN MEDIUM EXCESS AQUEOUS ALKALI OVER THAT REQUIRED TO NEUTRALIZE EXCESS SULFONATION ACID, SULFONIC ACID PRODUCT AND TO NEUTRALIZE HYDROGEN HALIDE WHICH RESULTS FROM DEHYDROHALOGENATION OF THE B-HALOETHYLARYL SULFONIC ACID, IN AMOUNT OF THE ORDER OF 2.1 MOLES OF ALKALI PER MOLE OF ADDED SULFUR TRIOXIDE, WATER PRESENT BEING IN AMOUNT SUFFICIENT TO GIVE THE DESIRED SOLUTION CONCENTRATION OF FINAL PRODUCT, DISTILLING OFF THE POLYCHLORINATED ALIPHATIC LIQUID HYDROCARBON, SEPARATING INSOLUBLE MATTER FROM THE REMAINING MIXTURE OF REACTION MEDIUM AND AQUEOUS ALKALI AND HEATING THE RESULTING AQUEOUS MIXTURE AT ABOUT 50* TO ABOUT 100*C. WHILE OXYGEN IS BUBBLED THERETHROUGH TO MINIMIZE POLYMER FORMATION UNTIL DEHYDROHALOGGENATON IS SUBSTANTIALLY COMPLETE. 